1. Field of the Invention
The present invention relates to a method of producing a semiconductor thin film and, more particularly, to a method of peeling a semiconductor thin film and a method of producing a solar cell using the semiconductor thin film.
2. Related Background Art
Known technology includes the formation of a semiconductor thin film through a peeling layer such as a porous layer or the like on a semiconductor substrate and thereafter peeling the semiconductor thin film away from the semiconductor substrate. Specific peeling methods include etching methods and mechanical peeling methods with application of external force.
As an example of the latter, Japanese Patent Application Laid-Open No. 7-302889 (CANON K.K.) describes the technique of forming a porous layer on a surface of a first silicon wafer, thereafter forming an epitaxial silicon layer thereon, bonding a second silicon wafer to the epitaxial silicon layer, further bonding plates to the respective silicon wafers, and then separating the plates from each other, thereby peeling the epitaxial silicon layer away from the first silicon wafer.
Japanese Patent Application Laid-Open No. 8-213645 (SONY CORP.) describes technology similar to the above, in particular, forming a porous layer on a surface of a single-crystal silicon substrate, thereafter epitaxially growing a pn junction (solar cell layers) thereon, bonding the back surface of the single-crystal silicon substrate to a jig with an adhesive, and also bonding another jig, for example, of metal, quartz, or the like to the side of the solar cell layers to be peeled off, and thereafter separating the two jigs from each other, thereby peeling the solar cell layers away from the silicon substrate.
In the peeling of the semiconductor thin film or the solar cell layers according to the conventional techniques, each of the silicon substrate side and the side of the semiconductor thin film to be peeled off is supported by the rigid body or by the flat plate with low flexibility. Thus, the bonded flat plates are separated from each other upon peeling. Therefore, considerable force is necessary for the peeling. This could result in damaging the semiconductor thin film. In addition, the above techniques require a step of applying and curing the adhesive for securing the substrate to the plate or to the jig, which decreases productivity. Further, the adhesive remains on the back surface of the substrate and the above techniques thus require a step of removing the adhesive in order to recycle the remaining substrate.